--- jsr166/src/jsr166y/Phaser.java 2010/12/01 17:20:41 1.65 +++ jsr166/src/jsr166y/Phaser.java 2010/12/04 15:25:08 1.68 @@ -75,18 +75,19 @@ import java.util.concurrent.locks.LockSu * * *
Termination. A phaser may enter a termination - * state in which all synchronization methods immediately return - * without updating phaser state or waiting for advance, and - * indicating (via a negative phase value) that execution is complete. - * Termination is triggered when an invocation of {@code onAdvance} - * returns {@code true}. The default implementation returns {@code - * true} if a deregistration has caused the number of registered - * parties to become zero. As illustrated below, when phasers control - * actions with a fixed number of iterations, it is often convenient - * to override this method to cause termination when the current phase - * number reaches a threshold. Method {@link #forceTermination} is - * also available to abruptly release waiting threads and allow them - * to terminate. + * state, that may be checked using method {@link #isTerminated}. Upon + * termination, all synchronization methods immediately return without + * waiting for advance, as indicated by a negative return + * value. Similarly, attempts to register upon termination have no + * effect. Termination is triggered when an invocation of {@code + * onAdvance} returns {@code true}. The default implementation returns + * {@code true} if a deregistration has caused the number of + * registered parties to become zero. As illustrated below, when + * phasers control actions with a fixed number of iterations, it is + * often convenient to override this method to cause termination when + * the current phase number reaches a threshold. Method {@link + * #forceTermination} is also available to abruptly release waiting + * threads and allow them to terminate. * *
Tiering. Phasers may be tiered (i.e., * constructed in tree structures) to reduce contention. Phasers with @@ -96,6 +97,16 @@ import java.util.concurrent.locks.LockSu * increase throughput even though it incurs greater per-operation * overhead. * + *
In a tree of tiered phasers, registration and deregistration of + * child phasers with their parent are managed automatically. + * Whenever the number of registered parties of a child phaser becomes + * non-zero (as established in the {@link #Phaser(Phaser,int)} + * constructor, {@link #register}, or {@link #bulkRegister}), the + * child phaser is registered with its parent. Whenever the number of + * registered parties becomes zero as the result of an invocation of + * {@link #arriveAndDeregister}, the child phaser is deregistered + * from its parent. + * *
Monitoring. While synchronization methods may be invoked
* only by registered parties, the current state of a phaser may be
* monitored by any caller. At any given moment there are {@link
@@ -273,12 +284,11 @@ public class Phaser {
private static int unarrivedOf(long s) {
int counts = (int)s;
- return (counts == EMPTY)? 0 : counts & UNARRIVED_MASK;
+ return (counts == EMPTY) ? 0 : counts & UNARRIVED_MASK;
}
private static int partiesOf(long s) {
- int counts = (int)s;
- return (counts == EMPTY)? 0 : counts >>> PARTIES_SHIFT;
+ return (int)s >>> PARTIES_SHIFT;
}
private static int phaseOf(long s) {
@@ -287,7 +297,7 @@ public class Phaser {
private static int arrivedOf(long s) {
int counts = (int)s;
- return (counts == EMPTY)? 0 :
+ return (counts == EMPTY) ? 0 :
(counts >>> PARTIES_SHIFT) - (counts & UNARRIVED_MASK);
}
@@ -339,41 +349,37 @@ public class Phaser {
*/
private int doArrive(boolean deregister) {
int adj = deregister ? ONE_ARRIVAL|ONE_PARTY : ONE_ARRIVAL;
- long s;
- int phase;
- while ((phase = (int)((s = state) >>> PHASE_SHIFT)) >= 0) {
+ final Phaser root = this.root;
+ for (;;) {
+ long s = (root == this) ? state : reconcileState();
+ int phase = (int)(s >>> PHASE_SHIFT);
int counts = (int)s;
- int unarrived = counts & UNARRIVED_MASK;
- if (counts == EMPTY || unarrived == 0) {
- if (reconcileState() == s)
+ int unarrived = (counts & UNARRIVED_MASK) - 1;
+ if (phase < 0)
+ return phase;
+ else if (counts == EMPTY || unarrived < 0) {
+ if (root == this || reconcileState() == s)
throw new IllegalStateException(badArrive(s));
}
else if (UNSAFE.compareAndSwapLong(this, stateOffset, s, s-=adj)) {
- if (unarrived == 1) {
- long n = s & PARTIES_MASK; // unshifted parties field
- int u = ((int)n) >>> PARTIES_SHIFT;
- Phaser par = parent;
- if (par != null) {
- par.doArrive(u == 0);
- reconcileState();
- }
- else {
- n |= (((long)((phase+1) & MAX_PHASE)) << PHASE_SHIFT);
- if (onAdvance(phase, u))
- n |= TERMINATION_BIT;
- else if (u == 0)
- n |= EMPTY; // reset to unregistered
- else
- n |= (long)u; // reset unarr to parties
- // assert state == s || isTerminated();
- UNSAFE.compareAndSwapLong(this, stateOffset, s, n);
- releaseWaiters(phase);
- }
+ if (unarrived == 0) {
+ long n = s & PARTIES_MASK; // base of next state
+ int nextUnarrived = ((int)n) >>> PARTIES_SHIFT;
+ if (root != this)
+ return parent.doArrive(nextUnarrived == 0);
+ if (onAdvance(phase, nextUnarrived))
+ n |= TERMINATION_BIT;
+ else if (nextUnarrived == 0)
+ n |= EMPTY;
+ else
+ n |= nextUnarrived;
+ n |= ((long)((phase + 1) & MAX_PHASE)) << PHASE_SHIFT;
+ UNSAFE.compareAndSwapLong(this, stateOffset, s, n);
+ releaseWaiters(phase);
}
- break;
+ return phase;
}
}
- return phase;
}
/**
@@ -411,7 +417,7 @@ public class Phaser {
break;
}
else {
- synchronized(this) { // 1st sub registration
+ synchronized (this) { // 1st sub registration
if (state == s) { // recheck under lock
par.doRegister(1);
do { // force current phase
@@ -490,15 +496,9 @@ public class Phaser {
/**
* Creates a new phaser with the given parent and number of
- * registered unarrived parties. Registration and deregistration
- * of this child phaser with its parent are managed automatically.
- * If the given parent is non-null, whenever this child phaser has
- * any registered parties (as established in this constructor,
- * {@link #register}, or {@link #bulkRegister}), this child phaser
- * is registered with its parent. Whenever the number of
- * registered parties becomes zero as the result of an invocation
- * of {@link #arriveAndDeregister}, this child phaser is
- * deregistered from its parent.
+ * registered unarrived parties. When the given parent is non-null
+ * and the given number of parties is greater than zero, this
+ * child phaser is registered with its parent.
*
* @param parent the parent phaser
* @param parties the number of parties required to advance to the
@@ -512,10 +512,10 @@ public class Phaser {
int phase = 0;
this.parent = parent;
if (parent != null) {
- Phaser r = parent.root;
- this.root = r;
- this.evenQ = r.evenQ;
- this.oddQ = r.oddQ;
+ final Phaser root = parent.root;
+ this.root = root;
+ this.evenQ = root.evenQ;
+ this.oddQ = root.oddQ;
if (parties != 0)
phase = parent.doRegister(1);
}
@@ -524,7 +524,7 @@ public class Phaser {
this.evenQ = new AtomicReference